Modern internal combustion engines typically have one or more combustion chambers with a piston movably mounted in, or mounted relative to, the combustion chamber. The piston is connected to an output device, such as a crankshaft. An air intake system provides air to each combustion chamber. A fuel system delivers fuel from a fuel supply through delivery lines to one or more fuel injectors. The fuel is mixed with air, and, after the piston compresses the fuel-air mixture, the fuel is ignited, causing combustion. The expansion of the combustion gases pushes the piston during the power stroke and causes movement of the output device.
A stock electronic control unit (ECU) includes a microprocessor that processes inputs and adjusts the air-fuel ratio by outputting a fuel injector control signal. The ECU typically monitors several key elements that are fundamental to combustion engines, for example, exhaust gas temperature, exhaust oxygen levels, throttle position, rpm's, torque, power requirements, engine temperature, manifold absolute pressure (MAP), outside air temperature and humidity, as well as other factors.
Generally, the stock ECU adjusts the timing of the engine fuel requirements based on a precise set of numbers loaded into look-up tables or maps within the ECU that have been pre-computed by the manufacturer for that particular vehicle. These are pre-computed based on stoichiometric or theoretical combustion in which the stoichiometric ratio of air to gasoline (air-fuel ratio) at the time of ignition is 14.7 to 1. The stock ECU outputs ECU pulses, each having particular characteristics, such as the fuel injector pulse width (the length of time the fuel injector remains open), the timing of the leading edge of each pulse, and the distance or interval between equivalent parts of adjacent pulses. The disadvantage of the use of a look-up table is that the pre-computed values are only optimal for an ideal, new engine. Particularly if significant aftermarket modifications (for example, adding or changing a turbocharger, adding or changing an intercooler, changing of the exhaust system, and modifying the intake system) are made to the vehicle's engine system, the pre-computed values will not provide optimum engine functionality or performance. To address the need to modify the stock ECU fuel delivery system, several add-on, aftermarket or secondary ECU's have been developed.
One such secondary ECU is disclosed in U.S. Pat. No. 8,996,279 issued to Dobeck. In this system, an attempt was made to optimize fuel delivery, but the method is only applicable during an open-loop power mode. The system uses two factors, the engine speed and whether the previous duration of the fuel injector control signal from the vehicle's ECU had time added to it or subtracted from it. Whether time is added to or subtracted from the current ECU duration is determined by (1.) whether the duration of the previous engine cycle was increased (had time added to the stock duration, so more fuel was given) or decreased (had time subtracted from the stock duration, so less fuel was given) and (2.) whether the engine speed increased or decreased. Though the Dobeck system may perform well at times, at other times it does not improve engine performance. For example, the Dobeck system continues to increase each duration output if the speed is increasing and if the immediately preceding duration had been increased, even though a point will be reached at which this system is reducing the performance. Additionally, the stock duration is typically on the lean side, and, the Dobeck system intermittently reduces this stock duration. The reduction below the stock duration often has an adverse effect on the engine performance.
Overall, the Dobeck system does not operate efficiently because the increase and decrease of speed does not correspond to the need for fuel in all situations. For example, in some situations, though the speed of the vehicle is increasing, the vehicle's fueling requirements may become less. In such situations, and regardless how slightly the vehicle's speed is increasing, the Dobeck system increases the amount of fuel given. If a vehicle engine speeds up while the vehicle goes downhill and if the duration had been increased, the Dobeck system again gives more fuel, even though the vehicle does not need more fuel. In other situations, if the speed of the engine is decreasing (no matter for what reason), the Dobeck system decreases the amount of fuel provided by the fuel injectors even when more fuel is needed for optimum performance. For example, when a vehicle is going up a very steep hill, the fuel requirements increase dramatically, even if the engine's speed may reduce due to lack of power. In this instance, the Dobeck system determines that the speed has decreased, so if the last duration was increased over the stock duration, the new duration time is decreased, even though the engine would perform better with more fuel.
The prior art add-on control systems are, at best, partial solutions. The prior art systems experience one or more of the following problems: all the sets of conditions experienced by an internal combustion engine are not addressed; performance is improved only at times; smooth transitions are not provided; and the already lean stock pulse width duration is decreased at times.
Accordingly, there is a need for a system that increases engine performance in more situations and in additional sets of conditions, provides smooth transitions between operational modes, and does not reduce the pulse width below the stock pulse width.